eletricty Flashcards Preview

PHYSICS > eletricty > Flashcards

Flashcards in eletricty Deck (9)
Loading flashcards...

current in series

current flows from negative to positive
however scientists draw it in the opposite direction, like it is flowing from positive to negative- conventional current
the current is the same all the way around


current in parallel

the current across all branches add up to the total current leaving the cell


pd in series

Total energy carried by the current is shared between the two lamps – why 2 lamps in one circuit are dimmer than 1 lamp because all of the energy is transferred to that one lamp so its brighter
Pd isn’t always shared evenly between components but the total pd across all components is the same as the pd across the cell
In series pd is split between the components


pd in parallel

In parallel the pd across each individual branch is the same as the pd supplied by the cell


resistance in series

resistors in series add together – the current has to pass through each resistor and can’t bypass them


resistance in parallel

the total resistance of 2 resistors in parallel is less than resistance of the smallest individual resistor. This is because in parallel we have 2 pathways for the current to take and so more total current will flow through the circuit. If current increases but pd hasn’t changed then resistance doesn’t change – v= I x r


why is live wire dangerous

Live wire is dangerous if touched. The earth is 0v. if you touched the wire a current would flow through the person into the earth and they would be electrocuted


danger of connection between wire and metal

If the live wire becomes loose and touches the metal case then the case cab become live and has pd of 230v. the earth wire is connected to the ground with a metal rod so if the case does become live a current flows into the earth and the fuse melts and shuts of the appliance. This prevents electric shocks


efficiency in ng

Energy is lost in the power cables due to the resistance of the wires. Transformers increase efficiency. The electricity passes through step up transformers which increase the pd. Less energy is lost in the power cables when pd is very high. A step down transformer reduces the pd to 230 v to homes
Step up transformers increase the pd, reducing energy loss in the transmission cables